Acute lymphoblastic leukemia

Prognostic significance of molecular-cytogenetic abnormalities in pediatric T-ALL is not explained by immunophenotypic differences

Pediatric T-cell acute lymphoblastic leukemia (T-ALL) is characterized by chromosomal rearrangements possibly enforcing arrest at specific development stages. We studied the relationship between molecular-cytogenetic abnormalities and T-cell development stage to investigate whether arrest at specific stages can explain the prognostic significance of specific abnormalities. We extensively studied 72 pediatric T-ALL cases for genetic abnormalities and expression of transcription factors, NOTCH1 mutations and expression of specific CD markers. HOX11 cases were CD1 positive consistent with a cortical stage, but as 4/5 cases lacked cytoplasmatic-beta expression, developmental arrest may precede beta-selection. HOX11L2 was especially confined to immature and pre-AB developmental stages, but 3/17 HOX11L2 mature cases were restricted to the gammadelta-lineage. TAL1 rearrangements were restricted to the alphabeta-lineage with most cases being TCR-alphabeta positive. NOTCH1 mutations were present in all molecular-cytogenetic subgroups without restriction to a specific developmental stage. CALM-AF10 was associated with early relapse. TAL1 or HOX11L2 rearrangements were associated with trends to good and poor outcomes, respectively. Also cases with high vs low TAL1 expression levels demonstrated a trend toward good outcome. Most cases with lower TAL1 levels were HOX11L2 or CALM-AF10 positive. NOTCH1 mutations did not predict for outcome. Classification into T-cell developmental subgroups was not predictive for outcome.

5,10-Methylenetetrahydrofolate reductase polymorphisms and acute lymphoblastic leukemia risk: a meta-analysis

There is evidence supporting a role for 5-10 methylenetetrahydrofolate reductase (MTHFR) gene variants in acute lymphoblastic leukemia (ALL). To provide a more robust estimate of the effect of MTHFR polymorphisms on the risk of ALL, we did a meta-analysis to reevaluate the association between the two most commonly studied MTHFR polymorphisms (C677T and A1298C) and ALL risk. All case-control studies investigating an association between the C677T or A1298C polymorphisms and risk of ALL were included. We applied both fixed-effects and random-effects models to combine odds ratio (OR) and 95% confidence intervals (95% CI). Q-statistic was used to evaluate the homogeneity and both Egger and Begg-Mazumdar tests were used to assess publication bias. The meta-analysis of the C677T polymorphism and risk of childhood ALL included 13 studies with a total of 4,894 individuals. Under a fixed-effects model, the TT genotype failed to be associated with a statistically significant reduction of childhood ALL risk (TT versus CT + CC: OR, 0.88; 95% CI, 0.73-1.06; P = 0.18). However, individuals homozygous for the 677T allele exhibited a 2.2-fold decrease in risk of adult ALL (TT versus CT + CC: OR, 0.45; 95% CI, 0.26-0.77; P = 0.004). In both cases, no evidence of heterogeneity was observed. No association between the A1298C variant and susceptibility to both adult and childhood ALL was disclosed. Our findings support the proposal that the common genetic C677T polymorphism in the MTHFR contributes to the risk of adult ALL, but not to the childhood ALL susceptibility.

HLA-identical haematopoietic stem cell transplantation for acute leukaemia in children: less relapse with higher biologically effective dose of TBI

To examine relapse, survival and transplant-related complications in relationship to disease- and pre-treatment-related characteristics, we evaluated 132 children, who consecutively received an allogeneic HLA-identical SCT for acute leukaemia in our centre: ALL in first remission (n=24), ALL in second remission (n=53) and AML in first remission (n=55). The source of the stem cells was bone marrow in all but three cases. Most patients (89%) were pre-treated with cyclophosphamide and an age-related dose of TBI. Initially, GVHD prophylaxis consisted of long-course MTX only (n=24), later short-course MTX and CsA (n=102) was given. All patients were nursed in strictly protective isolation and received total gut decontamination to suppress their potentially pathogenic enteric microflora. The 5-year probability of overall survival was 63, 53 and 74% for ALL1, ALL2 and AML1, respectively (median follow-up: 10.6 years). The overall transplant-related mortality was 6%. The incidence of acute GVHD was 17%; 6% was grades II-IV. A higher total biologically effective TBI dose (BED) resulted in a decreased relapse frequency (P=0.034) and increased overall survival. AML patients with acute GVHD got no relapse (P=0.02); this was not the case in ALL patients. Fractionated TBI regimens with higher BED should be evaluated in prospective studies.

Regulatory polymorphisms of multidrug resistance 1 (MDR1) gene are associated with the development of childhood acute lymphoblastic leukemia

The aim of this study is to determine whether the polymorphisms of the MDR1 gene are associated with the development of childhood acute lymphoblastic leukemia (ALL). The MDR1 gene polymorphisms, -2352 G>A, -934A>G, -692T>C (5' regulatory region) and 3435C>T (exon 26), were examined in 157 ALL patients and 96 healthy children. The amounts of MDR1 mRNA were quantified in 54 healthy individuals using normal peripheral blood mononuclear cells to evaluate the effect of each polymorphism on the gene expression. The frequency of the G/G genotype of the -2352 G>A was significantly higher in ALL than in controls (74/109 versus 52/96, p=0.04). The frequency of the T/T genotype of the 3435C>T was also significantly higher in ALL (29/118 versus 10/96, p=0.006). In a haplotype analysis using the 5' regulatory sites, the frequency of a certain haplotype was higher in ALL than in controls (59/90 versus 42/88, p=0.048). When the -2352G>A was examined in different age groups, patients aged six or older were found to have the G/G genotype more frequently than the controls (42/51 versus 52/96, p=0.0014), while no difference was observed in the younger age group. The amounts of MDR1 mRNA were significantly higher in either G/G or G/A genotype of the -2352 G>A than in A/A genotype (p=0.04). The present study suggests that the genetic background of MDR1 may be associated with the development of childhood ALL, possibly due to a quantitative change in the MDR1 gene resulting from genetic polymorphisms.

Screening for leukemia- and clone-specific markers at birth in children with T-cell precursor ALL suggests a predominantly postnatal origin

Childhood T-cell precursor acute lymphoblastic leukemia (TCP ALL) is an aggressive disease with a presumably short latency that differs in many biologic respects from B-cell precursor (BCP) ALL. We therefore addressed the issue of in utero origin of this particular type of leukemia by tracing oncogenic mutations and clone-specific molecular markers back to birth. These markers included various first- and second-hit genetic alterations (TCRD-LMO2 breakpoint regions, n = 2; TAL1 deletions, n = 3; Notch1 mutations, n = 1) and nononcogenic T-cell receptor rearrangements (n = 13) that were derived from leukemias of 16 children who were 1.5 to 11.2 years old at diagnosis of leukemia. Despite highly sensitive polymerase chain reaction (PCR) approaches (1 cell with a specific marker among 100,000 normal cells), we identified the leukemic clone in the neonatal blood spots in only 1 young child. These data suggest that in contrast to BCP ALL most TCP ALL cases are initiated after birth.

In vitro cytotoxicity of nelarabine, clofarabine and flavopiridol in paediatric acute lymphoblastic leukaemia

The in vitro efficacies of three new drugs--clofarabine (CLOF), nelarabine (NEL) and flavopiridol (FP) - were assessed in a panel of acute lymphoblastic leukaemia (ALL) cell lines. The 50% inhibitory concentration (IC50) for CLOF across all lines was 188-fold lower than that of NEL. B-lineage, but not T-lineage lines, were >7-fold more sensitive to CLOF than cytosine arabinoside (ARAC). NEL IC50 was 25-fold and 113-fold higher than ARAC in T- and B-lineage, respectively. T-ALL cells were eightfold more sensitive to NEL than B-lineage but there was considerable overlap. FP was more potent in vitro than glucocorticoids and thiopurines and at doses that recent phase I experience predicts will translate into clinical efficacy. Potential cross-resistance of CLOF, NEL and FP was observed with many front-line ALL therapeutics but not methotrexate or thiopurines. Methotrexate sensitivity was inversely related to that of NEL and FP. Whilst NEL was particularly effective in T-ALL, a subset of patients with B-lineage ALL might also be sensitive. CLOF appeared to be marginally more effective in B-lineage than T-ALL and has a distinct resistance profile that may prove useful in combination with other compounds. FP should be widely effective in ALL if sufficient plasma levels can be achieved clinically.

Prognostic significance of cytogenetically detected chromosome 21 anomalies in childhood acute lymphoblastic leukemia: a Pediatric Oncology Group study

Chromosome anomalies have been shown to have prognostic significance in children with acute lymphoblastic leukemia (ALL). Chromosome 21 was evaluated for its ability to predict outcome when found in either a single copy (the Mono21 group) or when involved in a structural aberration (the Misc21 group). Both anomalies were associated with an increased risk of failure for patients with standard-risk ALL, rather than higher-risk ALL. Event-free survival was 50.0% at 5 years and 48.4% at 8 years for standard-risk patients with Mono21+Misc21, compared with 77.8 and 75.5%, respectively, for standard-risk patients without these anomalies of chromosome 21. There was no significant difference in outcome between the Mono21 and the Misc21 group (P = 0.10). Mono21 and Misc21 were determined to be independently prognostic whether or not the primary leukemic clone had fewer than 45 chromosomes. The frequency of an adverse outcome was comparable to other poor prognosis subgroups such as hypodiploidy (<45 chromosomes), t(9;22), or t(4;11), all of which have been targeted for aggressive therapy even if the case is otherwise standard risk.

Acute leukemia in early childhood

Acute leukemia in early childhood is biologically and clinically distinct. The particular characteristics of this malignancy diagnosed during the first months of life have provided remarkable insights into the etiology of the disease. The pro-B, CD10 negative immunophenotype is typically found in infant acute leukemia, and the most common genetic alterations are the rearrangements of the MLL gene. In addition, the TEL/AML1 fusion gene is most frequently found in children older than 24 months. A molecular study on a Brazilian cohort (age range 0-23 months) has detected TEL/AML1+ve (N = 9), E2A/PBX1+ve (N = 4), PML/RARA+ve (N = 4), and AML1/ETO+ve (N = 2) cases. Undoubtedly, the great majority of genetic events occurring in these patients arise prenatally. The environmental exposure to damaging agents that give rise to genetic changes prenatally may be accurately determined in infants since the window of exposure is limited and known. Several studies have shown maternal exposures that may give rise to leukemogenic changes. The Brazilian Collaborative Study Group of Infant Acute Leukemia has found that mothers exposed to dipyrone, pesticides and hormones had an increased chance to give birth to babies with infant acute leukemia [OR = 1.48 (95%CI = 1.05-2.07), OR = 2.27 (95%CI = 1.56-3.31) and OR = 9.08 (95%CI = 2.95-27.96)], respectively. This review aims to summarize recent clues that have facilitated the elucidation of the biology of early childhood leukemias, with emphasis on infant acute leukemia in the Brazilian population.

Risk of Second Malignant Neoplasms After Childhood Leukemia and Lymphoma: An International Study

BACKGROUND

Survivors of childhood leukemia and lymphoma experience high risks of second malignant neoplasms. We quantified such risk using a large dataset from 13 population-based cancer registries.

METHODS

The registries provided individual data on cases of leukemia, Hodgkin lymphoma, and non-Hodgkin lymphoma occurring in children aged 0-14 years and on subsequent second malignant neoplasms for different time periods from 1943 to 2000. Risks of second malignant neoplasms were assessed through standardized incidence ratios (SIRs) and corresponding 95% confidence intervals (CIs), using the incidence rates in the general populations covered by the registries as a reference. Cumulative absolute risks were also calculated.

RESULTS

A total of 133 second malignant neoplasms were observed in 16,540 patients (12,731 leukemias, 1246 Hodgkin lymphomas, and 2563 non-Hodgkin lymphomas) after an average follow-up of 6.5 years. The most frequent second malignancies after leukemia were brain cancer (19 cases, SIR = 8.52, 95% CI = 5.13 to 13.3), non-Hodgkin lymphoma (nine cases, SIR = 9.41, 95% CI = 4.30 to 17.9), and thyroid cancer (nine cases, SIR = 18.8, 95% CI = 8.60 to 35.7); the most frequent after Hodgkin lymphoma were thyroid cancer (nine cases, SIR = 52.5, 95% CI = 24.0 to 99.6), breast cancer (six cases, SIR = 20.9, 95% CI = 7.66 to 45.4), and neoplasms of skin (non-melanoma) (six cases, SIR = 34.0, 95% CI = 12.5 to 74.0); and the most frequent after non-Hodgkin lymphoma were thyroid cancer (six cases, SIR = 40.4, 95% CI = 14.8 to 88.0) and brain cancer (four cases, SIR = 6.97, 95% CI = 1.90 to 17.9). Cumulative incidence of any second malignant neoplasm was 2.43% (95% CI = 1.09 to 3.78), 12.7% (95% CI = 8.29 to 17.2), and 2.50% (95% CI = 1.04 to 3.96) within 30 years from diagnosis of leukemia, Hodgkin lymphoma, and non-Hodgkin lymphoma, respectively.

CONCLUSIONS

This population-based study provides, to our knowledge, the most precise and up-to-date estimates for relative and absolute risks of second malignant neoplasms after childhood leukemia and lymphoma.

Divergent Mechanisms of Glucocorticoid Resistance in Experimental Models of Pediatric Acute Lymphoblastic Leukemia

Cell line models of glucocorticoid resistance in childhood acute lymphoblastic leukemia (ALL) almost invariably exhibit altered glucocorticoid receptor (GR) function. However, these findings are incongruous with those using specimens derived directly from leukemia patients, in which GR alterations are rarely found. Consequently, mechanisms of glucocorticoid resistance in the clinical setting remain largely unresolved. We present a novel paradigm of glucocorticoid resistance in childhood ALL, in which patient biopsies have been directly established as continuous xenografts in immune-deficient mice, without prior in vitro culture. We show that the GRs from six highly dexamethasone-resistant xenografts (in vitro IC(50) >10 micromol/L) exhibit no defects in ligand-induced nuclear translocation and binding to a consensus glucocorticoid response element (GRE). This finding contrasts with five commonly used leukemia cell lines, all of which exhibited defective GRE binding. Moreover, whereas the GRs of dexamethasone-resistant xenografts were transcriptionally active, as assessed by the ability to induce the glucocorticoid-induced leucine zipper (GILZ) gene, resistance was associated with failure to induce the bim gene, which encodes a proapoptotic BH3-only protein. Furthermore, the receptor tyrosine kinase inhibitor, SU11657, completely reversed dexamethasone resistance in a xenograft expressing functional GR, indicating that pharmacologic reversal of glucocorticoid resistance in childhood ALL is achievable.

The C-MYB locus is involved in chromosomal translocation and genomic duplications in human T-cell acute leukemia (T-ALL), the translocation defining a new T-ALL subtype in very young children

The C-Myb transcription factor is essential for hematopoiesis, including in the T-cell lineage. The C-Myb locus is a common site of retroviral insertional mutagenesis, however no recurrent genomic involvement has been reported in human malignancies. Here, we identified 2 types of genomic alterations involving the C-MYB locus at 6q23 in human T-cell acute leukemia (T-ALL). First, we found a reciprocal translocation, t(6;7)(q23;q34), that juxtaposed the TCRB and C-MYB loci (n = 6 cases). Second, a genome-wide copy-number analysis by array-based comparative genomic hybridization (array-CGH) identified short somatic duplications that include C-MYB (MYB(dup), n = 13 cases of 84 T-ALL, 15%). Expression analysis, including allele-specific approaches, showed stronger C-MYB expression in the MYB-rearranged cases compared with other T-ALLs, and a dramatically skewed C-MYB allele expression in the TCRB-MYB cases, which suggests that a translocation-driven deregulated expression may overcome a cellular attempt to down-regulate C-MYB. Strikingly, profiling of the T-ALLs by clinical, genomic, and large-scale gene expression analyses shows that the TCRB-MYB translocation defines a new T-ALL subtype associated with a very young age for T-cell leukemia (median, 2.2 years) and with a proliferation/mitosis expression signature. By contrast, the MYB(dup) alteration was associated with the previously defined T-ALL subtypes.

High-resolution genomic profiling of childhood ALL reveals novel recurrent genetic lesions affecting pathways involved in lymphocyte differentiation and cell cycle progression

Gross cytogenetic anomalies are traditionally being used as diagnostic, prognostic and therapeutic markers in the clinical management of cancer, including childhood acute lymphoblastic leukemia (ALL). Recently, it has become increasingly clear that genetic lesions driving tumorigenesis frequently occur at the submicroscopic level and, consequently, escape standard cytogenetic observations. Therefore, we profiled the genomes of 40 childhood ALLs at high resolution. We detected multiple de novo genetic lesions, including gross aneuploidies and segmental gains and losses, some of which were subtle and affected single genes. Many of these lesions involved recurrent (partially) overlapping deletions and duplications, containing various established leukemia-associated genes, such as ETV6, RUNX1 and MLL. Importantly, the most frequently affected genes were those controlling G1/S cell cycle progression (e.g. CDKN2A, CDKN1B and RB1), followed by genes associated with B-cell development. The latter group includes microdeletions of the B-lineage transcription factors PAX5, EBF, E2-2 and IKZF1 (Ikaros), as well as genes with other established roles in B-cell development, that is RAG1 and RAG2, FYN, PBEF1 or CBP/PAG. The fact that we frequently encountered multiple lesions affecting genes involved in cell cycle regulation and B-cell differentiation strongly suggests that both these processes need to be targeted independently and simultaneously to trigger ALL development.

Duplication of the MYB oncogene in T cell acute lymphoblastic leukemia

We identified a duplication of the MYB oncogene in 8.4% of individuals with T cell acute lymphoblastic leukemia (T-ALL) and in five T-ALL cell lines. The duplication is associated with a threefold increase in MYB expression, and knockdown of MYB expression initiates T cell differentiation. Our results identify duplication of MYB as an oncogenic event and suggest that MYB could be a therapeutic target in human T-ALL.

Microarray-based classification of a consecutive series of 121 childhood acute leukemias: prediction of leukemic and genetic subtype as well as of minimal residual disease status

Gene expression analyses were performed on 121 consecutive childhood leukemias (87 B-lineage acute lymphoblastic leukemias (ALLs), 11 T-cell ALLs and 23 acute myeloid leukemias (AMLs)), investigated during an 8-year period at a single center. The supervised learning algorithm k-nearest neighbor was utilized to build gene expression predictors that could classify the ALLs/AMLs according to clinically important subtypes with high accuracy. Validation experiments in an independent data set verified the high prediction accuracies of our classifiers. B-lineage ALLs with uncharacteristic cytogenetic aberrations or with a normal karyotype displayed heterogeneous gene expression profiles, resulting in low prediction accuracies. Minimal residual disease status (MRD) in T-cell ALLs with a high (>0.1%) MRD at day 29 could be classified with 100% accuracy already at the time of diagnosis. In pediatric leukemias with uncharacteristic cytogenetic aberrations or with a normal karyotype, unsupervised analysis identified two novel subgroups: one consisting mainly of cases remaining in complete remission (CR) and one containing a few patients in CR and all but one of the patients who relapsed. This study of a consecutive series of childhood leukemias confirms and extends further previous reports demonstrating that global gene expression profiling provides a valuable tool for genetic and clinical classification of childhood leukemias.

Effects of human monoclonal antibody 216 on B-progenitor acute lymphoblastic leukemia in vitro

BACKGROUND

Human monoclonal antibody (mAb) 216 is a naturally occurring IgM cytotoxic mAb that binds to a glycosylated epitope on the surface of B-lymphocytes. This study investigated if this mAb could bind and kill acute lymphoblastic leukemia (ALL) B-progenitor lymphoblasts in vitro. ALL cell lines were used to determine if combining mAb 216 with chemotherapeutic drugs would enhance killing and cell lines were used to measure cytotoxicity by mAb 216 with human complement.

PROCEDURE

Expression of cell surface markers and mAb 216 epitope on fresh and banked ALL bone marrow samples was determined by flow cytometry. Fresh lymphoblasts were incubated for 20 hr with mAb 216 without complement to measure cytotoxicity. Cytotoxicity of ALL cell lines incubated with mAb 216 and vincristine (VCR) or human complement was determined using flow cytometry.

RESULTS

Pre-B-ALL cells but not T-ALL cells are bound and killed by mAb 216. The combination of mAb 216 and VCR at sub-therapeutic levels demonstrated enhanced cytotoxicity beyond that observed for either agent alone. Incubation of mAb 216 with human complement increased cytotoxicity of ALL cell lines.

CONCLUSION

This increased cytotoxicity with chemotherapy and the functional ability of mAb 216 to use multiple pathways to induce cell death identify mAb 216 as a potentially novel therapeutic tool in the treatment of B-progenitor ALL. Based on the results from this preclinical study, a Phase I clinical trial with mAb 216 for the treatment of patients with relapsed or refractory B-lineage ALL is ongoing.

New therapeutic strategies for the treatment of acute lymphoblastic leukaemia

Although contemporary treatments cure more than 80% of children with acute lymphoblastic leukaemia (ALL), some patients require intensive treatment and many patients still develop serious acute and late complications owing to the side effects of the treatments. Furthermore, the survival rate for adults with ALL remains below 40%. Therefore, new treatment strategies are needed to improve not only the cure rate but also the quality of life of these patients. Here, we discuss emerging new treatments that might improve the clinical outcome of patients with ALL. These include new formulations of existing chemotherapeutic agents, new antimetabolites and nucleoside analogues, monoclonal antibodies against leukaemia-associated antigens, and molecular therapies that target genetic abnormalities of the leukaemic cells and their affected signalling pathways.

Polyamines and DNA methylation in childhood leukaemia

Both polyamine metabolism and DNA methylation play an important role in normal and malignant growth. Specific enzyme inhibitors or drugs that interfere with these metabolic pathways have proven to be potential anticancer agents. Since DNA methylation and polyamine metabolism depend on a common substrate, i.e. S-adenosylmethionine, interaction between both pathways can be expected. Little is known about the relationship between these pathways but studies are available indicating that polyamines and DNA methylation are directly or indirectly interconnected, metabolically as well as physiologically with respect to the regulation of cell growth, differentiation and cancer development. These considerations give rise to the possibility that, by targeting both pathways, a more profound and effective inhibitory effect on the growth of malignant cells can be achieved. In previous studies we showed that 6-MP (6-mercaptopurine) as well as MTX (methotrexate), well-known drugs in the treatment of acute lymphoblastic leukaemia, inhibit DNA methylation and induce apoptosis in malignant blood cells. Our recent results show that combined treatment with 6-MP, MTX and drugs interfering with polyamine metabolism has additive/synergistic effects on the growth, cell viability and/or apoptotic death of leukaemic cells. Such a combination therapy could have great clinical value for patients in which therapy using inhibitors of thiopurines/purine metabolism has failed.

Relapse in children with acute lymphoblastic leukemia involving selection of a preexisting drug-resistant subclone

Relapse following remission induction chemotherapy remains a barrier to survival in approximately 20% of children suffering from acute lymphoblastic leukemia (ALL). To investigate the mechanism of relapse, 27 matched diagnosis and relapse ALL samples were analyzed for clonal populations using polymerase chain reaction (PCR)-based detection of multiple antigen receptor gene rearrangements. These clonal markers revealed the emergence of apparently new populations at relapse in 13 patients. More sensitive clone-specific PCR revealed that, in 8 cases, these "relapse clones" were present at diagnosis and a significant relationship existed between presence of the relapse clone at diagnosis and time to first relapse (P < .007). Furthermore, in cases where the relapse clone could be quantified, time to first relapse was dependent on the amount of the relapse clone at diagnosis (r = -0.84; P = .018). This observation, together with demonstrated differential chemosensitivity between subclones at diagnosis, argues against therapy-induced acquired resistance as the mechanism of relapse in the informative patients. Instead these data indicate that relapse in ALL patients may commonly involve selection of a minor intrinsically resistant subclone that is undetectable by routine PCR-based methods. Relapse prediction may be improved with strategies to detect minor potentially resistant subclones early during treatment, hence allowing intensification of therapy.

Retroviral insertional mutagenesis identifies RUNX genes involved in chronic myeloid leukemia disease persistence under imatinib treatment

The kinase inhibitor imatinib mesylate targeting the oncoprotein Bcr-Abl has revolutionized the treatment of chronic myeloid leukemia (CML). However, even though imatinib successfully controls the leukemia in chronic phase, it seems not to be able to cure the disease, potentially necessitating lifelong treatment with the inhibitor under constant risk of relapse. On a molecular level, the cause of disease persistence is not well understood. Initial studies implied that innate features of primitive progenitor cancer stem cells may be responsible for the phenomenon. Here, we describe an assay using retroviral insertional mutagenesis (RIM) to identify genes contributing to disease persistence in vivo. We transplanted mice with bone marrow cells retrovirally infected with the Bcr-Abl oncogene and subsequently treated the animals with imatinib to select for leukemic cells in which the proviral integration had affected genes modulating the imatinib response. Southern blot analysis demonstrated clonal outgrowth of cells carrying similar integration sites. Candidate genes located near the proviral insertion sites were identified, among them the transcription factor RUNX3. Proviral integration near the RUNX3 promoter induced RUNX3 expression, and Bcr-Abl-positive cell lines with stable or inducible expression of RUNX1 or RUNX3 were protected from imatinib-induced apoptosis. Furthermore, imatinib treatment selected for RUNX1-expressing cells in vitro and in vivo after infection of primary bone marrow cells with Bcr-Abl and RUNX1. Our results demonstrate the utility of RIM for probing molecular modulators of targeted therapies and suggest a role for members of the RUNX transcription factor family in disease persistence in CML patients.

The pharmacogenetics research network: from SNP discovery to clinical drug response

The NIH Pharmacogenetics Research Network (PGRN) is a collaborative group of investigators with a wide range of research interests, but all attempting to correlate drug response with genetic variation. Several research groups concentrate on drugs used to treat specific medical disorders (asthma, depression, cardiovascular disease, addiction of nicotine, and cancer), whereas others are focused on specific groups of proteins that interact with drugs (membrane transporters and phase II drug-metabolizing enzymes). The diverse scientific information is stored and annotated in a publicly accessible knowledge base, the Pharmacogenetics and Pharmacogenomics Knowledge base (PharmGKB). This report highlights selected achievements and scientific approaches as well as hypotheses about future directions of each of the groups within the PGRN. Seven major topics are included: informatics (PharmGKB), cardiovascular, pulmonary, addiction, cancer, transport, and metabolism.

Glucocorticoid-induced granzyme A expression can be used as a marker of glucocorticoid sensitivity for acute lymphoblastic leukemia therapy

The ability of glucocorticoids (GC) to efficiently kill lymphoid cells has led to their inclusion in essentially all chemotherapy procedures used to treat acute lymphoblastic leukemia (ALL). GC sensitivity is an important prognostic factor in ALL treatment, and it is used to classify patients into risk groups. Clinical assessment for GC sensitivity is very time-consuming, however. We have recently found that granzyme A (GZMA) mediates GC-induced apoptosis in ALL-derived cell line 697. In this study we examined the correlation between GC sensitivity and GC-induced GZMA expression by using seven established cell lines derived from ALL patients. The apoptosis assay showed four cell lines were GC-sensitive and three were GC-resistant. GC treatment markedly enhanced GZMA expression in GC-sensitive cell lines only, and not in GC-resistant cell lines. GC-induced GZMA expression also correlated well with the amount of GC-induced apoptosis. GC-induced GZMA expression could thus be a useful early biomarker for "personalized" ALL therapy.

Ancestry and pharmacogenetics of antileukemic drug toxicity

Treatment-related toxicity in acute lymphoblastic leukemia (ALL) can not only be life threatening but may also affect relapse risk. In 240 patients, we determined whether toxicities were related to 16 polymorphisms in genes linked to the pharmacodynamics of ALL chemotherapy, adjusting for age, race (self-reported or via ancestry-informative markers), sex, and disease risk group (lower- vs higher-risk therapy). Toxicities (gastrointestinal, infectious, hepatic, and neurologic) were assessed in each treatment phase. During the induction phase, when drugs subject to the steroid/cytochrome P4503A pathway predominated, genotypes in that pathway were important: vitamin D receptor (odds ratio [OR], 6.85 [95% confidence interval [CI], 1.73-27.0]) and cytochrome P4503A5 (OR, 4.61 [95% CI, 1.11-19.2]) polymorphisms were related to gastrointestinal toxicity and infection, respectively. During the consolidation phase, when antifolates predominated, the reduced folate carrier polymorphism predicted gastrointestinal toxicity (OR, 10.4 [95% CI, 1.35-80.4]) as it also did during continuation (OR, 2.01 [95% CI, 1.06-4.11]). In all 3 treatment phases, a glucuronosyltransferase polymorphism predicted hyperbilirubinemia (P = .017, P < .001, and P < .001) and methotrexate clearance (P = .028), which was also independently associated with hyperbilirubinemia (P = .026). The genotype-phenotype associations were similar whether analyses were adjusted by self-reported race or ancestry-informative genetic markers. Germ-line polymorphisms are significant determinants of toxicity of antileukemic therapy.

Proportion of long-term event-free survivors and lifetime of adult patients not cured after a standard acute lymphoblastic leukemia therapeutic program

BACKGROUND

In adult acute lymphoblastic leukemia, treatment results generally are expressed in terms of overall survival or disease-free survival at 3 years. In this investigation, the authors attempted to express the results in terms of the proportion of long-term disease-free survivors and in terms of lifetime in patients who developed recurrent disease or died.

METHODS

Univariate and multivariate analyses were used to assess the influence of different covariates on the 2 result criteria in 922 participants in the Adult Acute Lymphoblastic Leukemia-94 multicenter trial.

RESULTS

The proportion of long-term survivors was 21.5% (95% confidence interval [95% CI], 18.1-25.4%) and was higher in women than in men. The proportion decreased with increasing age, white blood cell count, and lactate dehydrogenase level. The lowest proportion was observed in patients ages 44 years to 55 years (11.4%; 95% CI, 7-17.9%) and in patients with the t(9;22) BCR-ABL karyotype (13.4%; 95% CI, 8.8-19.8%), and the highest proportion was observed in patients with the t(4;11) MLL-AF4 karyotype (31.3%; 95% CI, 18.2-48.3%). The mean expected lifetime of patients who were not cured was 11.4 months (95% CI, 9.1-14.1 months). It was longer in men than in women and was shorter with increasing age, performance status, hemoglobin level, and white blood cell count.

CONCLUSIONS

The results of this study highlighted and specified the importance of some classic prognostic factors in patients with acute lymphoblastic leukemia.

Effect of race on outcome of white and black children with acute myeloid leukemia: the St. Jude experience

BACKGROUND

The association between race and outcome of treatment for childhood acute myeloid leukemia (AML) has not been adequately studied.

PROCEDURE

We compared the clinical characteristics, biological features, and outcomes between white and black children with AML who were treated on five consecutive clinical protocols (1980-2002) at St. Jude Children's Research Hospital. We used proportional hazards modeling to investigate the relation between race and outcome.

RESULTS

We observed no statistically significant differences between the 229 white and 58 black patients in clinical characteristics, FAB subtype, cytogenetic features, or outcome. There were no significant differences in event-free survival (EFS) or overall survival (OS) between the two race groups in individual clinical trials or in all studies combined. For the study group as a whole, the 5-year survival estimate was 39.2% +/- 3.6% for white patients and 33.8% +/- 6.5% for black patients. However, on our most recent trial (AML-97), there was a trend towards inferior outcome among black patients: the 5-year survival estimates were 55.6% +/- 12.3% and 27.3% +/- 13.5% for whites and blacks, respectively.

CONCLUSIONS

Although we detected no differences in treatment outcome between white and black children with AML over the entire study period, black children appear to have worse outcomes than white children during more recent studies. Improved treatment is needed for all children with AML.

Genetic studies of a cluster of acute lymphoblastic leukemia cases in Churchill County, Nevada

OBJECTIVE

In a study to identify exposures associated with 15 cases of childhood leukemia, we found levels of tungsten, arsenic, and dichlorodiphenyldichloroethylene in participants to be higher than mean values reported in the National Report on Human Exposure to Environmental Chemicals. Because case and comparison families had similar levels of these contaminants, we conducted genetic studies to identify gene polymorphisms that might have made case children more susceptible than comparison children to effects of the exposures.

DESIGN

We compared case with comparison children to determine whether differences existed in the frequency of polymorphic genes, including genes that code for enzymes in the folate and purine pathways. We also included discovery of polymorphic forms of genes that code for enzymes that are inhibited by tungsten: xanthine dehydrogenase, sulfite oxidase (SUOXgene), and aldehyde oxidase.

PARTICIPANTS

Eleven case children were age- and sex-matched with 42 community comparison children for genetic analyses. Twenty parents of case children also contributed to the analyses.

RESULTS

One bilalleleic gene locus in SUOX was significantly associated with either case or comparison status, depending on which alleles the child carried (without adjusting for multiple comparisons).

CONCLUSIONS

Although genetic studies did not provide evidence that a common agent or genetic susceptibility factor caused the leukemias, the association between a SUOXgene locus and disease status in the presence of high tungsten and arsenic levels warrants further investigation.

RELEVANCE

Although analyses of community clusters of cancer have rarely identified causes, these findings have generated hypotheses to be tested in subsequent studies.

A limited sampling strategy to estimate individual pharmacokinetic parameters of methotrexate in children with acute lymphoblastic leukemia

PURPOSE

The objectives of this study were to characterize the population pharmacokinetics of MTX in patients with acute lymphoblastic leukemia (ALL) with ages ranging from 2 to 16 years and to propose a limited sampling strategy to estimate individual pharmacokinetic parameters.

METHODS

Seventy-nine children were enrolled in this study; they received 1-4 courses of chemotherapy. MTX was administered at a dose of 5 g/m2. MTX population parameters were estimated from 61 patients (231 courses; age range: 2-16 years). The data were analyzed by nonlinear mixed-effect modeling with use of a two-compartment structural model. The interoccasion variability was taken into account in the model. Eighteen additional patients (70 courses) were used to evaluate the predictive performances of the Bayesian approach and to devise a limited sampling strategy.

RESULTS

The following population parameters were obtained: total clearance (CL) = 8.8 l/h (inter-individual variability: 43%), initial volume of distribution (V1) = 17.3 l (48%), k12 = 0.0225 h(-1) (41%), and k21 = 0.0629 h(-1) (24%). The inter-individual variability in the initial volume of distribution was partially explained by the fact that this parameter was weight-dependent. Intercourse variability was limited, with a mean variation of 13.2%. The protocol involving two sampling times, 24 and 48 h after the beginning of infusion, allows precise and accurate determination of individual pharmacokinetic parameters and consequently, it was possible to predict the time at which the MTX concentration reached the predicted threshold (0.2 microM) below which the administration of folinic acid could be stopped.

CONCLUSION

The results of this study combine the relationships between the pharmacokinetic parameters of MTX and patient covariates that may be useful for dose adjustment, with a convenient sampling procedure that may aid in optimizing pediatric patient care.

Leukemia-associated antigenic isoforms induce a specific immune response in children with T-ALL

The potential immunogenicity of acute lymphoblastic leukemia of the T cell (T-ALL), a small subgroup of childhood leukemia with increased risk for treatment failure and early relapse, was addressed by serological identification of leukemia-derived antigens by recombinant expression cloning (SEREX). Thirteen antigens with homology to known genes that are involved in critical cellular processes were detected. Further characterization of the 4 novel isoforms revealed that 3 (HECTD1Delta, CX-ORF-15Delta and hCAP-EDelta) had restricted mRNA expression in more than 70% of T-ALLs (n = 22) and that specific antibodies against these isoforms were detected in up to 30% of patients (n = 16), with the highest frequency for HECTD1Delta. The latter protein was present at high abundance in T-ALLs but not in normal hematopoietic tissues. Given that the leukemia-associated antigens detected in this study have an intracellular localization, the generation of immune effector responses most likely requires antigen presentation. To test this assumption, dendritic cells were loaded with HECTD1Delta protein and used for T cell stimulation. A specific T cell response was induced in vitro in all 3 healthy donors studied, including a former T-ALL patient. These data suggest that T-ALL may induce a specific cellular and humoral antileukemia immune response in children, thereby supporting new approaches for immunotherapy.

Wnt3A activates canonical Wnt signalling in acute lymphoblastic leukaemia (ALL) cells and inhibits the proliferation of B-ALL cell lines

Acute lymphoblastic leukaemia (ALL) is the most common malignancy in children. Recently, there has been a growing interest in Wnt signalling in several aspects of cellular development, including cancer formation. Little is known about Wnt signalling in B-ALL. We investigated whether activation of canonical Wnt signalling could occur in B-ALL cells and thereby play a potential role in cellular growth and/or survival. This study found that Wnt3A induced beta-catenin accumulation in both primary B-ALL cells and B-ALL leukaemia cell lines. Further, Wnt3A was shown to induce nuclear translocation of beta-catenin and TCF/Lef-1 dependent transcriptions in the B-ALL cell line Nalm-6. Examination of the mRNA expression pattern of WNT ligands, FZD receptors and WNT antagonists in Nalm-6 cells identified a set of ligands and receptors available for signalling, as well as antagonists potentially available for modulating the response. Functional analyses showed that Wnt3A inhibited the proliferation of several, but not all, B-ALL cell lines studied. Finally, microarray analysis was used to identify several Wnt3A target genes involved in a diverse range of cellular activities, which are potential mediators of the Wnt3A-restrained proliferation.

Influence of socioeconomic status on childhood acute lymphoblastic leukemia treatment in Indonesia

OBJECTIVE

A major reason for poor survival of childhood acute lymphoblastic leukemia in developing countries is treatment refusal or abandonment. This can be associated with parental socioeconomic status and attitudes of health care providers. Our study examined the influence of 2 socioeconomic status determinants, parental income and education, on treatment in an Indonesian academic hospital.

METHODS

Medical charts of 164 patients who received a diagnosis of acute lymphoblastic leukemia between 1997 and 2002 were abstracted retrospectively. Data on treatment results and parental financial and educational background were collected. Open interviews were conducted with parents and health care providers.

RESULTS

Of all patients, 35% refused or abandoned treatment, 23% experienced treatment-related death, 22% had progressive or relapsed leukemia, and 20% had an overall event-free survival. Treatment results differed significantly between patients with different socioeconomic status; 47% of poor and 2% of prosperous patients refused or abandoned treatment. Although poor and prosperous patients used the same protocol, the provided treatment differed. Poor patients received less individualized attention from oncologists and less structured parental education. Strong social hierarchical structures hindered communication with doctors, resulting in a lack of parental understanding of the necessity to continue treatment. Most poor patients could not afford treatment. Access to donated chemotherapy also was inadequate. Treatment refusal or abandonment frequently resulted. There was no follow-up system to detect and contact dropouts. Health care providers were not fully aware that their own attitude and communication skills were important for ensuring compliance of patients and parents.

CONCLUSIONS

Children's survival of acute lymphoblastic leukemia in developing countries could improve if problems that are associated with parental financial and educational background and medical teams' attitudes to treatment and follow-up could be addressed better.

RNAi-mediated silencing of TEL/AML1 reveals a heat-shock protein- and survivin-dependent mechanism for survival

The TEL/AML1 fusion gene results from the most frequent t(12;21)(p13;q22) translocation in childhood acute lymphoblastic leukemia (ALL). Its contribution to transformation is largely unknown, in particular with respect to survival and apoptosis. We therefore silenced TEL/AML1 expression in leukemic REH cells by RNA inhibition, which eventually led to programmed cell death. Microarray and 2D gel electrophoresis data demonstrated a differential regulation of heat-shock proteins (HSPs), among them HSP90, as well as of its client, survivin. Consistent with these findings, ectopic expression of TEL/AML1 in Ba/F3 cells increased protein levels of HSP90 and survivin and conferred resistance to apoptotic stimuli. Our data suggest that TEL/AML1 not only contributes to leukemogenesis by affecting an antiapoptotic network but also seems to be indispensable for maintaining the malignant phenotype. The functional relationship between TEL/AML1, HSP90, and survivin provides the rational for targeted therapy, be it the fusion gene or the latter 2 proteins.

Post-treatment intellectual functioning in children treated for acute lymphoblastic leukaemia (ALL) with chemotherapy-only: A prospective, sibling-controlled study

Intellectual functioning (verbal, performance and full-scale IQ) in 43 children treated for acute lymphoblastic leukaemia (ALL) with chemotherapy-only was evaluated in a nationwide, prospective, sibling-controlled study. Intellectual assessment was performed at diagnosis and repeated shortly after cessation of 2 years treatment, including intrathecal and systemic chemotherapy. Using hierarchical regression analysis, patients' and siblings' (n=27) scores were longitudinally analysed and compared to assess possible changes and differences over time. At both assessments, before and after treatment, the patients showed average scores on intelligence tests compared to population norms. Longitudinal analysis and cross-sectional comparisons revealed no significant differences between patients and controls. Young patients showed a small relative decline, albeit not significant, on performance-IQ compared to healthy siblings. Despite intensive and potentially neurotoxic treatment, no evident negative effects on intelligence were found. However, it cannot be precluded that younger patients are at risk for a small decline in PIQ.

Glucocorticoid resistance in two key models of acute lymphoblastic leukemia occurs at the level of the glucocorticoid receptor

Glucocorticoids (GCs) specifically induce apoptosis in malignant lymphoblasts and are thus pivotal in the treatment of acute lymphoblastic leukemia (ALL). However, GC-resistance is a therapeutic problem with an unclear molecular mechanism. We generated approximately 70 GC-resistant sublines from a GC-sensitive B- and a T-ALL cell line and investigated their mechanisms of resistance. In response to GCs, all GC-resistant subclones analyzed by real-time polymerase chain reaction (PCR) showed a deficient up-regulation of the GC-receptor (GR) and its downstream target, GC-induced leucine zipper. This deficiency in GR up-regulation was confirmed by Western blotting and on retroviral overexpression of GR in resistant subclones GC-sensitivity was restored. All GC-resistant subclones were screened for GR mutations using denaturing high-pressure liquid chromatography (DHPLC), DNA-fingerprinting, and fluorescence in situ hybridization (FISH). Among the identified mutations were some previously not associated with GC resistance: A484D, P515H, L756N, Y663H, L680P, and R714W. This approach revealed three genotypes, complete loss of functional GR in the mismatch repair deficient T-ALL model, apparently normal GR genes in B-ALLs, and heterozygosity in both. In the first genotype, deficiency in GR up-regulation was fully explained by mutational events, in the second by a putative regulatory defect, and in the third by a combination thereof. In all instances, GC-resistance occurred at the level of the GR in both models.

Clinical, cytogenetic and molecular characteristics of 14 T-ALL patients carrying the TCRβ-HOXA rearrangement: a study of the Groupe Francophone de Cytogénétique Hématologique

Recently, we and others described a new chromosomal rearrangement, that is, inv(7)(p15q34) and t(7;7)(p15;q34) involving the T-cell receptor beta (TCRbeta) (7q34) and the HOXA gene locus (7p15) in 5% of T-cell acute lymphoblastic leukemia (T-ALL) patients leading to transcriptional activation of especially HOXA10. To further address the clinical, immunophenotypical and molecular genetic findings of this chromosomal aberration, we studied 330 additional T-ALLs. This revealed TCRbeta-HOXA rearrangements in five additional patients, which brings the total to 14 cases in 424 patients (3.3%). Real-time quantitative PCR analysis for HOXA10 gene expression was performed in 170 T-ALL patients and detected HOXA10 overexpression in 25.2% of cases including all the cases with a TCRbeta-HOXA rearrangement (8.2%). In contrast, expression of the short HOXA10 transcript, HOXA10b, was almost exclusively found in the TCRbeta-HOXA rearranged cases, suggesting a specific role for the HOXA10b short transcript in TCRbeta-HOXA-mediated oncogenesis. Other molecular and/or cytogenetic aberrations frequently found in subtypes of T-ALL (SIL-TAL1, CALM-AF10, HOX11, HOX11L2) were not detected in the TCRbeta-HOXA rearranged cases except for deletion 9p21 and NOTCH1 activating mutations, which were present in 64 and 67%, respectively. In conclusion, this study defines TCRbeta-HOXA rearranged T-ALLs as a distinct cytogenetic subgroup by clinical, immunophenotypical and molecular genetic characteristics.

Alterations in gamma-actin and tubulin-targeted drug resistance in childhood leukemia

BACKGROUND

Proteomic investigations have revealed alterations in cytoskeletal proteins expressed in human acute lymphoblastic leukemia cells that are resistant to microtubule-disrupting agents. We characterized gamma-actin expression in antimicrotubule drug-resistant leukemia and examined the effect of altered gamma-actin in resistance of acute lymphoblastic leukemia to antimicrotubule agents.

METHODS

Two-dimensional polyacrylamide gel electrophoresis and mass spectrometry were used to identify actin proteins in human acute lymphoblastic leukemia cell lines resistant to vinblastine (CCRF-CEM/VLB100 cells) and desoxyepothilone B (CCRF-CEM/dEpoB140 cells). Fluorescence-based cycle sequencing was used to detect gene mutations. Site-directed mutagenesis was used to generate mutant gamma-actin expression plasmids, which were used to transfect mouse NIH/3T3 cells. Clonogenic analysis was used for drug sensitivity studies. A small interfering RNA (siRNA) was used to block gamma-actin gene expression in human neuroblastoma SH-EP cells. Expression of gamma-actin (normalized to that of beta2-microglobulin [beta2M]) in primary leukemia cells obtained from patients at diagnosis (n = 44) and relapse (n = 25) was examined using semiquantitative reverse transcription-polymerase chain reaction. Statistical significance of changes in the ratio of gamma-actin to beta2M expression between diagnosis and relapse samples was determined by two-sided unpaired Student's t tests.

RESULTS

We identified novel mutant forms of gamma-actin and the concomitant loss of wild-type gamma-actin in CCRF-CEM/VLB100 cells and CCRF-CEM/dEpoB140 cells. Mouse NIH/3T3 cells that expressed the mutant gamma-actin proteins were more resistant to antimicrotubule agents than cells transfected with empty plasmid. Human neuroblastoma SH-EP cells transfected with gamma-actin siRNA displayed higher relative resistance to paclitaxel (P<.001), vinblastine (P = .04), and epothilone B (P = .045) than mock-transfected cells. No gamma-actin gene mutations were identified in 37 samples of primary leukemia cells (eight from patients at diagnosis, 29 from patients at relapse). Gamma-actin gene expression was lower in acute lymphoblastic leukemia samples collected at clinical relapse (n = 25; mean gamma-actin/beta2M = 0.53) than in samples collected at diagnosis (n = 44; mean gamma-actin/beta2M = 0.68; difference = 0.15, 95% confidence interval [CI] = 0.04 to 0.27, P = .01).

CONCLUSIONS

These data provide functional and associative clinical evidence of a novel form of drug resistance that involves interactions between gamma-actin and microtubules.

Influence of genetic polymorphisms on the risk of developing leukemia and on disease progression

BACKGROUND

Recent studies have provided evidence that common genetic variations with low penetrance could account for a proportion of leukemia and could also influence disease outcome, although the results obtained are still controversial.

MATERIAL AND METHODS

We reviewed 54 recent reports focused on the contribution of genetic polymorphisms to the risk of developing leukemia and to disease progression. The polymorphisms of genes encoding drug-metabolising enzymes (CYP family, NQO1, GSTT1, GSTM1, GSTP1), enzymes involved in folate metabolism (MTHFR, TYMS, SHMT1, MTRR), and DNA repair enzymes (XPD, XPG, RAD51, XRCC1, XRCC3, CHEK2, ATM) were considered in the review.

RESULTS

There was a good agreement on the influence of NQO1*2 polymorphism and those of the enzymes involved in DNA repair with the increased risk of therapy-related leukemia/myelodysplastic syndrome. Most studies found a strong association between the polymorphisms MTHFR, C677T or A1298C, and NQO1*2 or *3 and the risk of acute lymphoblastic leukemia (ALL). In addition, most of the studies reported an association between GSTT1 deletions and an increased risk of de novo acute myeloid leukemia. In ALL, polymorphisms in the genes of folate metabolism are associated with poor prognosis, and the 3R3R TYMS polymorphism in particular is associated with methotrexate resistance.

CONCLUSION

The reports reviewed support the hypothesis that several low-penetrance genes with multiplicative effects together with dietary effects, ambient exposition, and individual immune system responses, may account for the risk of leukaemia.

TEL-AML1 transgenic zebrafish model of precursor B cell acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a clonal disease that evolves through the accrual of genetic rearrangements and/or mutations within the dominant clone. The TEL-AML1 (ETV6-RUNX1) fusion in precursor-B (pre-B) ALL is the most common genetic rearrangement in childhood cancer; however, the cellular origin and the molecular pathogenesis of TEL-AML1-induced leukemia have not been identified. To study the origin of TEL-AML1-induced ALL, we generated transgenic zebrafish expressing TEL-AML1 either ubiquitously or in lymphoid progenitors. TEL-AML1 expression in all lineages, but not lymphoid-restricted expression, led to progenitor cell expansion that evolved into oligoclonal B-lineage ALL in 3% of the transgenic zebrafish. This leukemia was transplantable to conditioned wild-type recipients. We demonstrate that TEL-AML1 induces a B cell differentiation arrest, and that leukemia development is associated with loss of TEL expression and elevated Bcl2/Bax ratio. The TEL-AML1 transgenic zebrafish models human pre-B ALL, identifies the molecular pathways associated with leukemia development, and serves as the foundation for subsequent genetic screens to identify modifiers and leukemia therapeutic targets.

Translating microarray data for diagnostic testing in childhood leukaemia

Background

Recent findings from microarray studies have raised the prospect of a standardized diagnostic gene expression platform to enhance accurate diagnosis and risk stratification in paediatric acute lymphoblastic leukaemia (ALL). However, the robustness as well as the format for such a diagnostic test remains to be determined. As a step towards clinical application of these findings, we have systematically analyzed a published ALL microarray data set using Robust Multi-array Analysis (RMA) and Random Forest (RF).

Methods

We examined published microarray data from 104 ALL patients specimens, that represent six different subgroups defined by cytogenetic features and immunophenotypes. Using the decision-tree based supervised learning algorithm Random Forest (RF), we determined a small set of genes for optimal subgroup distinction and subsequently validated their predictive power in an independent patient cohort.

Results

We achieved very high overall ALL subgroup prediction accuracies of about 98%, and were able to verify the robustness of these genes in an independent panel of 68 specimens obtained from a different institution and processed in a different laboratory. Our study established that the selection of discriminating genes is strongly dependent on the analysis method. This may have profound implications for clinical use, particularly when the classifier is reduced to a small set of genes. We have demonstrated that as few as 26 genes yield accurate class prediction and importantly, almost 70% of these genes have not been previously identified as essential for class distinction of the six ALL subgroups.

Conclusion

Our finding supports the feasibility of qRT-PCR technology for standardized diagnostic testing in paediatric ALL and should, in conjunction with conventional cytogenetics lead to a more accurate classification of the disease. In addition, we have demonstrated that microarray findings from one study can be confirmed in an independent study, using an entirely independent patient cohort and with microarray experiments being performed by a different research team.

The Thalidomide Analogue, CC-4047, Induces Apoptosis Signaling and Growth Arrest in Childhood Acute Lymphoblastic Leukemia Cells In vitro and In vivo

PURPOSE

Thalidomide and its analogues have shown promise in the treatment of multiple myeloma but their therapeutic potential has not been evaluated in models of acute lymphoblastic leukemia (ALL).

EXPERIMENTAL DESIGN

We assessed the effects of the thalidomide analogue, CC-4047, on the growth and apoptosis signaling of human B cell precursor (BCP) ALL cell lines and freshly obtained childhood BCP-ALL cells grown with or without stromal cells. In addition, we studied the effects of CC-4047 on the progression and dissemination of xenotransplanted human BCP-ALL cells in nonobese diabetic/severe combined immunodeficiency mice.

RESULTS

CC-4047 reduced the proliferation of human BCP-ALL cell lines in vitro. In contrast with the antileukemic effect of cytarabin, this was more pronounced when cell lines or freshly obtained childhood BCP-ALL cells were cocultured with stromal cells. CC-4047 induced the cleavage of caspase-3, caspase-9, and poly(ADP-ribose) polymerase in stroma-cocultured BCP-ALL cells. The inhibition of tumor growth, caspase-3 cleavage, and reduced microvessel density was observed in nonobese diabetic/severe combined immunodeficiency mice inoculated s.c. with childhood BCP-ALL cells upon CC-4047 treatment. After i.v. BCP-ALL xenotransplantation, CC-4047 reduced splenic dissemination.

CONCLUSIONS

The thalidomide analogue, CC-4047, displays profound cytostatic effects on stroma-supported human ALL cells both in vitro and in vivo.

Expression of Livin, an antiapoptotic protein, is an independent favorable prognostic factor in childhood acute lymphoblastic leukemia

Livin, a member of the inhibitor of apoptosis proteins, has been considered to be a poor prognostic marker in malignancies. However, little is known about the clinical relevance of Livin expression in childhood acute lymphoblastic leukemia (ALL). In this study, the expression of Livin was analyzed in 222 patients with childhood ALL using quantitative reverse transcriptase–polymerase chain reaction (RT-PCR) to investigate a possible association with the clinical features at diagnosis and treatment outcomes. Both Livin expression rates and expression levels were higher in patients with favorable prognostic factors. The expression rate was also higher in patients with a favorable day 7 bone marrow response to induction chemotherapy (P < .001). The Livin expression was related to the absence of relapse (P < .001). Similarly, the relapse-free survival rate (± 95% CI) was higher in patients with Livin expression than in patients without Livin expression (97.9% ± 4.0% versus 64.9% ± 11.8%, P < .001). Multivariate analysis for relapse-free survival demonstrated that Livin expression was an independent favorable prognostic factor in childhood ALL (P = .049). This study suggests that Livin expression is a novel prognostic marker in childhood ALL and thus needs to be incorporated into the patient stratification and treatment protocols.

[Twenty years of treating childhood acute lymphoblastic leukemia]

BACKGROUND

Conventional prognostic factors for relapse in patients with acute lymphoblastic leukemia (ALL) are the main basis of risk-stratified treatments.

OBJECTIVES

To analyze conventional risk factors for relapse and design a predictive model for relapse in our series, after 20 years of experience in treating ALL.

PATIENTS AND METHOD

We performed a multivariate analysis of conventional prognostic factors in the treatment of ALL in our unit and compared them with the risk groups in the Berlin-Frankfurt-Münster (BFM-ALL) treatment protocols.

RESULTS

Between 1984 and 2004, 232 children were diagnosed with ALL and treated according to the different versions of the BFM protocols (BFM83, BFM86, BFM90 and BFM95) at the Hospital Niño Jesús, Madrid, Spain. The event-free survival for all patients was 79.4 % (95 % CI: 72.7-85.4). Overall survival among patients who relapsed was 10.72 % (95 % CI: 6-27.3). The only significant prognostic factor for relapse identified by multivariate analysis was leukocyte [white blood cell (WBC)] count higher than 80,000/ml at diagnosis (hazard ratio [HR]: 4.63; 95 % CI: 1.61-13.3; p 5 0,004). The sensitivity and specificity of WBC in predicting relapses were 31.4 % and 87.5 %, respectively. The sensitivity and specificity of BFM risk group stratification in predicting relapses were 25 and 85.9 respectively.

CONCLUSIONS

A leukocyte count at diagnosis higher than 80,000/ml and BFM risk-stratified treatment have insufficient sensitivity and specificity to identify relapses.

The Bcr-Abl mutations T315I and Y253H do not confer a growth advantage in the absence of imatinib

Mutations in the Bcr-Abl kinase domain are a frequent cause of imatinib resistance in patients with advanced CML or Ph+ ALL. The impact of these mutations on the overall oncogenic potential of Bcr-Abl and on the clinical course of the disease in the absence of imatinib is presently unclear. In this study, we analyzed the effects of the Bcr-Abl P-loop mutation Y253H and the highly imatinib resistant T315I mutation on kinase activity in vitro and transforming efficiency of Bcr-Abl in vitro and in vivo. Immunoprecipitated Bcr-AblY253H and Bcr-AblT315I proteins displayed similar kinase activities and substrate phosphorylation patterns as Bcr-Abl wildtype. We directly compared the proliferative capacity of mutant to wildtype Bcr-Abl in primary BM cells in vitro and in a murine transplantation model of CML by using a competitive repopulation assay. The results implicate that in the absence of imatinib, there is no growth advantage for cells carrying Bcr-AblT315I or Bcr-AblY253H compared to Bcr-Ablwt, whereas imatinib treatment clearly selects for leukemic cells expressing mutant Bcr-Abl both in vitro and in vivo. Thus, the analysed Bcr-Abl mutants confer imatinib resistance, but do not induce a growth advantage in the absence of imatinib.